Evaluating the effects of membrane filtration on sensory and chemical properties of wine

Luke Bohanan, Jeff Strekas, Roger Boulton, Hildegarde Heymann, and David E. BlockDepartment of Viticulture and EnologyUniversity of California, Davis

Why study filtration?

Some winemakers believe that this process may strip subtle aromas and flavors from the finished wine.

Many winemakers argue that this process is not only bad for the wine but actually unnecessary. Others find it is essential for clarity and stability.

Some winemakers choose not to filter to avoid robbing the wine of its true character

Clarity

Microbial Stability

Need a systematic study to examine the effects of filtration

Objectives

Investigate any transient changes in chemical composition during filtration

Investigate the extent of oxygen pickup during the filtration process

Evaluate the sensory and chemical impact of sterile cartridge filtration on red and white wines

Cabernet SauvignonCabernet Sauvignon

Control – No Filtration

Filtration Through Empty

Housing

Filtration Through 0.45

µm PVDF Filter

Filtration Through 0.45 µm PES Filter

Chemical AnalysisSensory Analysis

Time Points:0 Weeks3 Week5 Weeks7 Weeks9 Weeks…

Rep

1

Rep

1

Rep

2

Rep

3

Rep

1

Rep

2

Rep

3

Rep

1

Rep

2

Rep

3

• Push with nitrogen (no pump)• Filter right into bottling line• Extended one run of PVDF to

look at transient behavior

• 2007 Sonoma Valley• Post ML, oak aging

Color changes are minimal during one filtration/bottling

A420* A520* Color Hue* Color Density*Least Significant Difference 0.028 0.0309 0.0037 0.0569

Bottles 97-98 0.3805A 0.4427A 0.8597BC 0.8232A

Bottles 133-134 0.3790A 0.4408A 0.8599BC 0.8198A

Bottles 24-25 0.3692AB 0.4302AB 0.8582C 0.7993AB

Bottles 4-5 0.3612AB 0.4227AB 0.8545D 0.7838AB

Bottles 50-51 0.3600AB 0.4178AB 0.8616BC 0.7778AB

Bottles 73-74 0.3597AB 0.4155AB 0.8656A 0.7752AB

Bottles 13-14 0.3513B 0.4090B 0.8590BC 0.7603B

Bottles 36-37 0.3503B 0.4063B 0.8621AB 0.7567B

* Different superscripts denote a significant difference at alpha = 0.05Each reported value is an average of six replicates

Table 2. Color changes during one filtration run

Color changes are minimal during one filtration/bottling

Bottle Number

0 20 40 60 80 100 120 140

Col

or P

aram

eter

0.0

0.2

0.4

0.6

0.8

1.0

A420 A520 Hue Density

Tannin changes during one filtration/bottling

Tannin*mg catechin eq/L

Least Significant Difference 18.209

Bottles 36-37 238.369A

Bottles 73-74 234.368AB

Bottles 133-134 230.577AB

Bottles 50-51 226.222AB

Bottles 97-98 225.059AB

Bottles 4-5 221.117AB

Bottles 24-25 219.803B

Bottles 13-14 218.152B

*Different superscripts denote a significant difference at alpha = 0.05Each reported value is an average of six reps

Table 3. Tannin changes during filtration run

Tannin changes are minimal during one filtration/bottling

Bottle Number

0 20 40 60 80 100 120 140

Ta

nn

in (

mg c

ata

ech

in e

q/L

)

0

50

100

150

200

250

300

Figure 2. Tannin as a function of bottle number. Bottles were sampled from the bottling line during the course of filtration with a PVDF membrane filter. Tannin was measured on a sample from each bottle using the Adams-Harbertson Assay.

Not much difference during filtration—Now let’s examine differences between the filtration treatments

Sensory characteristics evaluated

Table 1. Flavor, Mouthfeel, and Aroma Standard CompositionsStandard Composition

Bitter 0.75 g caffeine*Sour 1.5 g citric acid*Sweet 3.5 g sucrose*Astringent 312 mg alum*High-Viscocity 30 g/L Polycose*Low-Viscocity H2OBerry/Currant 1 sliced strawberry, 3 sliced raspberry, 3 sliced blackberry, 5 mL cassis**Cherry 10 canned bing cherries, 3 tsp cherry juice, 2 tsp cherry pie filling**Dried Fruit 15 raisins, 2 sliced prunes, 1 sliced apricot**

Vegetal1 cm2 green bell pepper, 2 cut string beans, 1 tsp canned asparagus juice, 1 tsp canned green bean juice, 5 blades grass**

Spice 1/8 tsp cinnamon, 1/8 tsp all spice, 3 cloves**Black Pepper 1/8 tsp ground black pepper**

Floral2.5 mL of 1 drop rose essence in 200 mL H2O, 2.5 mL of 1 drop violet essence in 200 mL H2O**

Leather/Smoke 3x1 cm pieces of leather shoe lace, 1/8 tsp liquid smoke**Solvent/Chemical 1 drop nail polish remover in 10 mL H2O**Oak 3 small American oak chips**Vanilla 5 mL Vanilla flavoring**Chocolate 1.5 chopped chocolate chips**Hot/Ethanol 15 mL vodka**

* added to 1L H2O** added to 50 mL Franzia Cabernet Sauvignon

Sensory ANOVA

Table 4. Repeated Measures ANOVA Results

Pr>F Value Time Time*Filter Time*Rep Time*JudgeBerry/Currant 0.0835 0.1272 0.0163* <0.0001*Cherry <0.0001* 0.2252 0.9941 <0.0001*Dried Fruit <0.0001* 0.5785 0.8705 <0.0001*Vegetal <0.0001* 0.6287 0.2929 <0.0001*Spice 0.0095* 0.7531 0.936 <0.0001*Black Pepper 0.0016* 0.9479 0.3753 <0.0001*Floral <0.0001* 0.5798 0.4427 <0.0001*Leather/Smoke <0.0001* 0.8235 0.0278* <0.0001*Solvent/Chemical <0.0001* 0.4957 0.5963 <0.0001*Oak <0.0001* 0.0191* 0.3618 <0.0001*Vanilla 0.0003* 0.3555 0.9706 <0.0001*Chocolate 0.0016* 0.8618 0.5329 <0.0001*Hot/Ethanol <0.0001* 0.9904 0.8951 <0.0001*Astringent <0.0001* 0.1419 0.5326 <0.0001*Bitter <0.0001* 0.4845 0.7347 <0.0001*Sour <0.0001* 0.8656 0.923 <0.0001*Viscous 0.0014* 0.4533 0.1336 <0.0001** Value is significant at alpha = 0.05

Spider plot of sensory attributes

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W0

EMP W0

PES W0

PVD W0

0

0.5

1

1.5

2

2.5

3

3.5

4Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W3

EMP W3

PES W3

PVD W3

0

0.5

1

1.5

2

2.5

3

3.5

4Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W5

EMP W5

PES W5

PVD W5

0

0.5

1

1.5

2

2.5

3

3.5

4Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W7

EMP W7

PES W7

PVD W7

0

0.5

1

1.5

2

2.5

3

3.5

4Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W9

EMP W9

PES W9

PVD W9

0 weeks 3 weeks 5 weeks

9 weeks7 weeks

Figure 1. The ef fect of sterile f iltration on Cabernet Sauvignon. All treatments including the control change over time in the bottle. However, there are few signif icant dif ferences between the treatments at any given time point.

Sensory attributes of Cabernet are not affected by filtration

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W0

EMP W0

PES W0

PVD W0

0

0.5

1

1.5

2

2.5

3

3.5

4Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W3

EMP W3

PES W3

PVD W3

0

0.5

1

1.5

2

2.5

3

3.5

4Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W5

EMP W5

PES W5

PVD W5

0

0.5

1

1.5

2

2.5

3

3.5

4Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W7

EMP W7

PES W7

PVD W7

0

0.5

1

1.5

2

2.5

3

3.5

4Berry

Cherry

DrFruit

Vegetal

Spice

Pepper

Floral

Leath/Sm

SolventOak

Vanilla

Choc

EtOH

Bitter

Astrin

Sour

Visc

CTL W9

EMP W9

PES W9

PVD W9

0 weeks 3 weeks 5 weeks

9 weeks7 weeks

Figure 1. The ef fect of sterile f iltration on Cabernet Sauvignon. All treatments including the control change over time in the bottle. However, there are few signif icant dif ferences between the treatments at any given time point.

Cabernet changes over time—but not with filtration treatment

BerryA

CherryA

DrFruitA

VegetalA

SpiceA

BlPepprA

FloralA

LeathSmA

SolChemA

OakAVanillaA

ChocoA

EthanolA

BitterT

AstrinT

SourT

ViscousT

CTL0

EMP0

PES0PVD0

CTL3

EMP3

PES3

PVD3

CTL5EMP5

PES5

PVD5

CTL7EMP7

PES7PVD7 CTL9

EMP9

PES9

PVD9

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

-1.5 -1 -0.5 0 0.5 1

CV2(

17.6

%)

CV1(40.9%)

Figure 5. Canonical Variate Analysis (CVA) of sensory properties of Cabernet Sauvignon after filtration. This CVA plot illustrates distinct difference over time with very little difference as a function of filtration treatment.

Filtration treatment does not affect color density

A420* A520* Color Hue* Color Density*

Least Significant Difference 0.0491 0.0567 0.0043 0.1058A

Day 1 PVDF 0.3841A 0.4455A 0.8616A 0.8297A

Day 3 PVDF 0.3510A 0.4077A 0.8610A 0.7587A

Day 2 PES 0.3490A 0.4053A 0.8610A 0.7543A

Day 1 PES 0.3670A 0.4267A 0.8602AB 0.7937A

Day 2 PVDF 0.3790A 0.4408A 0.8599AB 0.8198A

Day 3 PES 0.3765A 0.4382A 0.8596AB 0.8147A

Day 3 No Filter 0.3516A 0.4092A 0.8596AB 0.7608A

Day 1 No Filter 0.3791A 0.4412A 0.8594AB 0.8203A

Day 1 Control 0.3510A 0.4097A 0.8566B 0.7607A

Day 2 No Filter 0.3633A 0.4243A 0.8562B 0.7877A

* Different superscripts denote a significant difference at alpha = 0.05Each reported value is an average of six replicates

Table 5. Color as a function of filtration treatment

Filtration does not affect tannin

Tannin*mg catechin eq/L

Least Significant Difference 20.868

Day 1 PES 232.42A

Day 2 PES 231.03A

Day 1 No Filter 230.84A

Day 2 PVDF 230.58A

Day 3 No Filter 230.35A

Day 1 Control 230.16A

Day 1 PVDF 227.20A

Day 3 PES 226.56A

Day 3 PVDF 225.58A

Day 2 No Filter 217.85A

*Different superscripts denote a significant difference at alpha = 0.05Each reported value is an average of six reps

Table 6. Tannin as a function of filtration treatment

Merlot PlanMerlot

Control – No Filtration

Filtration Through Pad

Filter

Filtration Through Pad

and 1 µm Depth Filter

Filtration Through Pad, 1 µm Depth,

and 0.45 µm PVDF Filter

Time Points:1Weeks2 Week4 Weeks6 Weeks12 Weeks16 Weeks…

Rep

1

Rep

1

Rep

2

Rep

3

Rep

1

Rep

2

Rep

3

Rep

1

Rep

2

Rep

3

Filtration Through Pad, 1 µm Depth, and 0.45 µm PES

Filter

Rep

1

Rep

2

Rep

3

Chemical AnalysisSensory Analysis

• 2009 Oakville• Post ML, oak aging

• Push with nitrogen (no pump)• Filter right into bottling line

Sensory attributes do not change as a function of filtration treatment

1 MxBerryA2 MCherryA3 FrVegA4 CookVegA5 HerbalA6 BkPepprA7 EarthyA8 VanillaA9 CdBoardA

10 ChemA11 SourT12 BitterT13 AstrinT14 ViscousT15 AlcoholT

AstringentViscousity

Alcohol/Heat

KeyMixed Berry

Medicial CherryFresh Vegitable

Cooked VegitableHerbal

Black PepperEarthy

Vanilla/oakCard Board Chemical

SourBitter

0.000

1.000

2.000

3.000

4.000

5.0001

2

3

4

5

6

7

89

10

11

12

13

14

15

Week 1

CTL

DEP

PAD

PES

VDF

0.000

1.000

2.000

3.000

4.000

5.0001

2

3

4

5

6

7

89

10

11

12

13

14

15

Week 2

CTL

DEP

PAD

PES

VDF

0.000

1.000

2.000

3.000

4.000

5.0001

2

3

4

5

6

7

89

10

11

12

13

14

15

Week 4

CTL

DEP

PAD

PES

VDF

0.000

1.000

2.000

3.000

4.000

5.0001

2

3

4

5

6

7

89

10

11

12

13

14

15

Week 6

CTL

DEP

PAD

PES

VDF

Two more time points—minimal differences

0.000

1.000

2.000

3.000

4.000

5.0001

2

3

4

5

6

7

89

10

11

12

13

14

15

Week 12

CTL

DEP

PAD

PES

VDF

0.000

1.000

2.000

3.000

4.0001

2

3

4

5

6

7

89

10

11

12

13

14

15

Week 16

CTL

DEP

PAD

PES

VDF

Summary

Very few differences noted during filtration for color and tannin-no transient is obvious

So far, no major differences observed between filtered and unfiltered wine

Still completing chemical studies on red wines

Completed Week 4 of sensory panel for White Wine.

Acknowledgments

Chik Brenneman Paul Green Jennifer Heelan Ron Runnebaum Tarit Nimmanwudipong Sensory Panelists Rodger Pachelbel

Gallo Sonoma Silverado Vineyards

American Vineyard Foundation